ok sorry if someone else said this but I have not read this theory yet.
jack has to be new leader of the island he even said this season when hurley asked "why did you come back" jack said because he thought the island can change him. After jack visited the light house he seems like Jacob to me. Jacob said on beach to Richard that he didn’t want to tell him he wanted him to figure it out on his own. That what jack did unlike hurley, Jacob didn’t tell jack what to do he just realized it like Jacob wanted him to do.
Jack I think he has giving up on everything besides the island he is a man of fate now I think he knows whatever he is supposed to do on that island he is going to do no matter how much he tires not to its his destiny.
Isn’t that what this season was called destiny found.
Jack has found his destiny and its to be new leader of island. its only fitting the two man who have not seen eye to eye on show would be the two on the island Jack and Locke. Just like MIB and Jacob have not seen eye to eye. for a long time.....
perfect ending in my book.....